Only include real files in package

```
❯ npx np minor
? The following new files will not be part of your published package:
- .github/workflows/test.yml
- .vscode/settings.json
- jest.config.js
- lib/Prediction.test.js
- lib/ReplicateClient.test.js
- lib/Version.test.js
The following new files will be published the first time:
- lib/errors.js
- lib/Prediction.js
- lib/ReplicateClient.js
- lib/ReplicateObject.js
- lib/utils.js
- lib/Version.js
Continue? (y/N)
```

Author: erbridge

package.json

@@ -8,6 +8,9 @@
   "license": "Apache-2.0",
   "main": "index.js",
   "type": "module",
+  "files": [
+    "lib/**/!(*.test.js)"
+  ],
   "scripts": {
     "test": "REPLICATE_API_TOKEN=not-a-real-token node index.js && NODE_OPTIONS=--experimental-vm-modules jest"
   },